Study On The Extraction,antioxidant Activity And Stability Of Curcumin

Turmeric is the dry rhizome of Curcuma longa L. Modern pharmacology show that its main ingredients curcumin has many physiological activities, such as anti-virus, anti-inflame, anti-cancer and anti-oxidation. The optimum conditions of solvent-refluxing extraction for curcumin were obtained by single-factor and orthogonal experiments. The optimum conditions of ultrasonic-microwave synergistic extraction for curcumin were obtained by single-factor and Box-Behnken design. Their DPPH·scavenging ability and hydroxyl radical scavenging ability were tested. The effect of light, heat, pH, metallic ions, food additives, oxidant and reductant on the stability of curcumin were studied. The preparation of microencapsulation curcumin byβ-cyclodextrin inclusion technology and the stability of microencapsulation curcumin were studied. The main experimental conclusions were as follows:The comparative results of two different extraction method were listed as follows. The extraction yield of curcumin is 2.97% under the optimum solvent-refluxing extraction conditions of extraction solvent 75%(v/v) ethanol, ratio of material to solvent 1:15 (g/mL), extraction temperature 75℃, extraction time 2.5 h and extraction times 2. The extraction yield of curcumin is 3.51% under the optimum ultrasonic-microwave synergistic extraction conditions of extraction solvent 75%(v/v) ethanol, material-solvent ratio 1:17 (g/mL), extraction temperature 53℃, extraction time 19 min and extracting times 2. The ultrasonic-microwave synergistic extraction is a modern extraction technology with the characteristics of time-saving and high efficiency.The experimental results of antioxidant activity of curcumin were listed as follows. Curcumin is capable to scavenge DPPH radical and hydroxyl radical. IC50 values of scavenging DPPH radical of curcumin, TBHQ and VC were 35.72μg/mL, 18.32μg/mL,21.17μg/mL, respectively, and the sequence of DPPH radical scavenging ability was TBHQ> VC> curcumin. IC50 values of scavenging hydroxyl radical of curcumin, TBHQ and VC were 19.20μg/mL,9.66μg/mL,36.56μg/mL, respectively, and the sequence of hydroxyl radical scavenging ability was TBHQ> curcumin> VC. The experimental results showed that curcumin has significant antioxidant functions.Stability of curcumin has been studied. Curcumin is relatively stable in the solution with pH< 4.0, however, when PH reaches 8, its degradation rate increases obviously, and its color changes from yellow to red. The thermal degradation rate of curcumin was minimum under low temperature, which increases as the temperature goes up. The photodegradation rate of curcumin increases as magnitude of the sunlight goes up, so the curcumin should be kept from the light. Sodium benzoate,NaCl and VC have little influence on the stability of curcumin, but Fe3+,Cu2+ H2O2,Na2SO3 have great influence on the stability of curcumin, Fe3+ and Cu2+ can make the curcumin solution produce precipitation when its concentration is slightly high.Complex of curcumin withβ-cyclodextrin, and its performance has been investigated. The optimum conditions of (3-cyclodextrin curcumin complex were inclusion temperature 50℃, inclusion time 1.5 h, the ratio of curcumin toβ-cyclodextrin 1:30, the embedding rate of curcumin was 87.34%。The water solubility of curcumin was greatly increased after curcumin inclusioned withβ-cyclodextrin. The stability of complex against light, heat, and oxidant was improved on some degree.